1. Field of the Invention
The present invention relates to a diaphragm for use in a fluid pump, accumulator, pressure regulator, or similar device wherein the diaphragm separates one fluid from another, and functions to equalize the fluid pressures within the device on each side of the diaphragm.
2. Description of the Prior Art
Fluid pumps of the reciprocating type are generally driven by another fluid, usually compressed air. These reciprocating fluid pumps utilize opposing pairs of pistons, bellows, diaphragms, etc. that separate the pumping fluid (i.e., compressed air) from the pumped fluid (e.g., water, acids, chemicals, potable liquids, etc.). In these reciprocating-type pumps, compressed air is alternately applied to commonly the outside surface of one diaphragm, then the outside surface of the opposite diaphragm in order to shift both diaphragms back and forth. The pumped fluid enters and exits the fluid pump at the opposite sides of each diaphragm (the insides) in response to the reciprocal action of each diaphragm to first, draw pump fluid into the fluid pump body, then exhaust the pumped fluid from the fluid pump body. Typical of the diaphragms utilized in such reciprocating pumps are shown in U.S. Pat. Nos. 4,634,350, 3,749,127, and 5,634,391.
An accumulator, sometimes referred to as a pressure regulator, generally comprises a hollow closed pressure vessel with a flexible diaphragm therein that divides the interior of the hollow pressure vessel into two separate cavities. One of the cavities is commonly filled with compressed air in a manner to exert pressure on the flexible diaphragm, thereby exerting this pressure on the fluid to be regulated which is contained in the other cavity of the accumulator on the oppose side of the diaphragm. Typical diaphragms as used in accumulators/pressure regulators are shown in U.S. Pat. Nos. 5,062,455, 2,339,876, 3,168,907, 2,300,722, 5,291,822, and 3,083,943.
As illustrated in all of the above-mentioned patents, the diaphragms generally comprise a central portion and a periphery portion that is commonly fitted between opposing mating metal shells that define the fluid pump housing or body, pressure regulator body, or accumulator pressure vessel. In fluid pumps, commonly the central portions of the diaphragms are more rigid, and are attached to oppose ends of a pump shifting rod. In such cases, the diaphragms flex in an annular area between the central, more rigid portion of the diaphragm and the periphery portion of the diaphragm. In accumulator/pressure regulator vessels or housings, the diaphragms generally comprise a central flexible portion and a periphery portion that, as in the pump housings, is fixed between two mating metal shells of the accumulator or pressure vessel. In designs as this, the entire central portion of the diaphragm is flexible and is intended to flex within the pressure vessel during normal use.
As these various prior art diaphragms flex and reciprocate within their respective housings, stress points occur at the corner edges of the device housings. These corner edges are indicated in FIGS. 1 and 2 by the numeral 2. FIGS. 1 and 2 are sections of prior art devices using conventional designs of diaphragms.
Those skilled in the art will appreciate that continued flexure of the diaphragms at the stress points of the diaphragms adjacent the device housing corner edges 2 will result in premature fatigue and failure of the diaphragms at these locations. It can also be appreciated that typical diaphragms are circular in configuration, and therefore, that the fatigue points in the diaphragms adjacent the device housing corner edges are not true "points", but rather, take the form of circles having diameters slightly less than the inside diameter of the device housing.
FIGS. 3 and 4 are figures similar to FIGS. 1 and 2, respectively, that illustrate attempts made to lessen the stress at the stress points (stress circles) of typical flexible diaphragms used in these various environments. Typically, as shown in FIG. 3, the corner edges of the device housing that clamp onto the diaphragm periphery are beveled at various angles (45.degree. being common) in order to eliminate the sharp circular edge of the device housing, and permit the diaphragm to flex at a larger radius of curvature at its flex point (flex circle), thereby significantly reducing stress at the specific diaphragm stress circles.
FIG. 4 illustrates another design for eliminating the sharp corner edges of the device housing, specifically forming these edges with rounded surfaces 6. These rounded surfaces, although more expensive to machine or form, totally eliminate the sharp edge surfaces by making a rounded transition from one surface to its mating 90.degree. surface, without the introduction of two corner edges in the 45.degree. beveled transition surface of the edge shown in FIG. 3.
In some instances, these design changes shown in FIGS. 3 and 4 were effective in reducing the instances of diaphragm failure at the specific stress circles adjacent the diaphragm periphery where it mounts to the device housing. In other instances, these designs actually created additional problems that: (1) affected the integrity of the system wherein the specific device (fluid pump, pressure regulator, etc.) was utilized; and (2) essentially only postponed the deterioration and failure of the particular diaphragms at their stress circles. This situation is illustrated in FIGS. 3 and 4. Specifically, in the instances wherein the diaphragm is used with a reciprocating fluid pump, when the pumped fluid is a solvent, acid, cleaner, or other liquid that is susceptible to solidification, solidified particles of the pumped liquid, dissolved or suspended contaminants, etc. tend to collect in the area of little or no fluid movement, specifically in the area adjacent the diaphragm/device housing mounting. This area is identified as numeral 8 in FIG. 4.
Those skilled in the art will readily appreciate that as these solidified particles or contaminants build up in the indicated area 8, two negative situations can occur. The first is that the build-up of these solidified particles can accumulate and grow to the point of effectively filling in the material that was cut away by the 45.degree. bevel 4 or curved surface 6, to the degree that the accumulation of solidified particles causes the deterioration and failure of the diaphragm at the stress circles, in a manner essentially identical to the process that occurs in the designs shown in FIGS. 1 and 2. Secondly, repeated oscillating contact of the diaphragm against this build-up of solidified particulate matter from the pumped fluid can also cause the build-up of particulate matter to break free from the build up in relatively large solid particles, which are then pumped with the fluid for its particular application. In certain applications, these relatively large free solid matter particles are detrimental to the peculiar process involved, and also contribute to premature deterioration and failure of delicate fluid seals in the fluid pump and other mechanisms downstream that come in contact with the fluid.